Plugging devices are used in oil and/or gas wells for sealing an upper section of the well from a lower section of the well. Such plugging devices comprise one or two anchoring devices and a sealing device. The anchoring device provides anchoring of the plugging device to the inner surface of the well. The sealing device comprises a sealing element and supporting devices for sealing the upper and lower sections of the well from each other, thereby preventing fluid from passing between the sections.
The plugging device is first run into the well in a run or radially retracted state by using a setting tool. At the desired location in the well, the plugging device is set in the well by actuating the plugging device to a set or radially expanded state, in which the anchoring device and sealing element are brought into contact with the well pipe. The supporting devices are supporting the sealing element, thereby preventing extrusion of the sealing element due to the pressure difference between the upper and lower sections.
After use, the plugging device may be retrieved from the well by using a retrieval tool. First, the pressure difference between the upper and lower section of the well is equalized. Then the anchoring device and sealing device are brought to a retrieval, or radially retracted, state, in which the plugging device may be pulled out of the well. Such plugging devices are known for example US 2004194969.
Junk catching devices are also used in oil and/or gas wells for catching junk, i.e. to prevent junk such as debris, metal fragments, metal parts or other unwanted objects to travel (i.e. fall or sink) further down into the well. Such unwanted objects are often also referred to as “fish”, as such objects must be fished or picked up from the well before other types of operations can be performed. If not, these objects may present obstructions which may prevent well tools from passing their location in the well.
It is known to use a junk catching device above plugging devices, such as bridge plugs, straddle packers etc. in order to prevent drilling fluid to enter the annular space between the plugging devices and the inner surface of the well pipe. Such well fluid tend to precipitate solid matter over time, and if the solid matter reaches the anchoring device or supporting devices for the sealing element of the plugging devices, then the plugging device may be difficult to retrieve from the well. Such situations may occur of it is necessary to interrupt an offshore oil/gas well due to bad weather conditions, where it may take several weeks to continue the well operation.
The problem with the use of such junk catching devices together with the plugging device is, first of all, that it requires several running operations in the well. First, the plugging device is run into the well and set, then the junk catching device is run into the well and set. During retrieval, first the retrieval tool for the junk catching device must be inserted into the well and the junk catching device must be retrieved, then the retrieval tool for the plugging device is inserted into the well and the plugging device must be retrieved.
Another problem is that well fluids and junk often will fall onto the plugging device during the retrieval of the junk catching device and during the insertion of the retrieval tool for the plugging device. Hence, the effect of the junk catching device is reduced. Consequently, a bailing operation may still be required between the retrieval of the junk catching device and the retrieval of the plugging device.
The object of the present invention is to provide a well tool where the above disadvantages are avoided. Hence, the object is to reduce the number of operations needed during setting and retrieval of the well tool, and to reduce the risk of the plugging device being stuck in the well.